The present invention relates to a thrust reverser for a turbofan-type turbojet engine in which movable thrust reverser doors change the direction of the flow of the air passing through the cold-flow air duct to provide the requisite thrust reversing forces.
Turbofan-type turbojet engines are well known in the art and, typically, comprise an annular housing concentrically surrounding the turbojet engine housing to define an annular cold-flow air duct extending along the longitudinal axis of the engine. A fan, driven by the turbojet engine, is located in the upstream portion of the cold-flow air duct so as to force air through the duct to augment the thrust of the turbojet engine.
In turbofan-type turbojet engines having a relatively high bypass ratio, a thrust reversing device may be associated with the annular housing to redirect the air passing through the cold-flow air duct to provide the thrust reversing forces. It is known to provide one or more pivotable thrust reversing doors in the annular housing to redirect the cold flow air to provide the necessary thrust reversing forces.
A typical prior art installation is illustrated in FIGS. 1, 2a and 2b and comprises annular housing 1, a thrust reverser 2 and a downstream housing portion 3. Housing 1 comprises an outer surface panel 4 and an inner surface panel 5 interconnected by frame structure 6. Similarly, downstream housing portion 3 has an inner surface panel 3a and an outer surface panel 3b.
The thrust reverser 2, comprising a pivotable door 7, extends between housing portion 1 and the downstream housing portion 3 so as to normally cover a generally laterally facing opening when the turbofan engine operates in the forward thrust mode. In this mode, the outer door panel 9 is substantially flush with the outer surface panel 4 and the outer downstream surface panel 3b to provide a smooth air flow, indicated by arrow 10, over the exterior of the housing.
An actuating cylinder 7a is supported on frame structure 6 and has an extendible and retractable piston rod attached to the internal structure 12 of the thrust reverser door 7. Internal structure 12 interconnects the outer door panel 9 with the inner door panel 11, which are also connected at their upstream edges by baffle member 13.
In known fashion, extension of the piston rod of actuator 7a causes the door 7 to pivot with respect to the housing such that its upstream end portion extends outwardly and its downstream end portion extends inwardly to block off the air flow 15 flowing through the cold-flow air duct. The air is redirected by the door outwardly through the lateral opening defined by the annular housing to provide a thrust reversing force.
FIG. 2a illustrates a turbofan engine having the known thrust reverser with the doors 7 in their closed positions, as illustrated in cross section in FIG. 1. The doors 7 are indicated in their opened positions in FIG. 2b during the thrust reversing process. During the thrust reversing operation, a deflection edge 8, extending from the inner housing panel 5, minimizes the turbulence of the air passing outwardly through the opening. Baffle member 13 imparts a forward vector to the air passing through the lateral opening to maximize the efficiency of the door in the thrust reversing mode. In order to maximize the efficiency, baffle member 13 must extend beyond the surface of inner panel 11
When the door 7 is in its closed position, as illustrated in FIG. 1, an internal cavity 16 is formed, bounded by the inner door panel 11, the baffle 13, the deflection edge 8 and a theoretical air flow line 14 extending between the inner surface panel 5 and the inner surface 3a of the downstream housing portion 3. Line 14 represents the ideal theoretical air flow through the cold flow air duct. The presence of cavity 16 causes disturbances in the air 15 flowing through the cold-flow air duct, thereby reducing its efficiency in the forward thrust mode.
Typical examples of such known thrust reversing systems may be found in French Patent 2,559,838 and in U.S. Pat. Nos. 4,410,152 and 4,485,970.
In order to resolve this problem, it has been proposed to provide a movable baffle member on the upstream end of the thrust reverser door, as evidenced in French Patent 2,618,853. While this solution allows the inner door panel to be positioned so as to minimize or eliminate the cavity 16, its structure is more complex.